Toyota accelerations revisited—hanging by a (tin) whisker

A NASA paper delivered at the International Tin Whisker Symposium last year reported on tin whisker growth in Toyota accelerator pedal position sensors that, depending on pedal rate of movement, could lead to unintended acceleration.

The whiskers were found in a "failed" sensor from a 2003 Camry and at least two other similar units that did not malfunction. The sensor in question was used on the Camry from 2002 to 2006 model years, and the specific Camry with the defective sensor (which was furnished to NASA) had 82,000 miles on it. The vehicle owner reported the car as "undrivable," with throttle response as: "I couldn't get any 'gas', and then the car would jerk forward at a rapid rate." The sensor had at least 17 whiskers in it, only one of which shorted contacts.

While the inspected sensors noted above could be typical of the entire lot, these incidents of whisker growth and shorting give cause for safety concern across the industry.

The NASA paper gives further insight by detailing tin whisker physical behavior as well as outlining guidelines and methods of detecting whiskers. But rather than summarize the report here, readers can access the easily read, but complete, 30 page NASA presentation by clicking here.

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It's amazing how something so small, like a tin whisker would cause the car to be so undrivable. If toyota does not confront this issue head on, they could soon see many angry car owners sending their cars back for a refund. They already had some trouble a few years back with this safety issue, and I cannot imagine that they haven't learnt their lesson.
Thomas - http://www.carid.com/

If such a huge effort was put into RoHS development and the failure rate is so small, then why are some industries with high reliability requirements (e.g. Military) EXEMPT? Also, I have yet to find a definitive explanation on what causes whisker growth and how the growth rate is affected by environmental and other factors. I've read some studies but there tend to be contradictions between and sometimes within the studies.
I've seen tin whiskers inside a crystal package that shorted out the crystal. SEM pictures showed a whisker fragment that had broken off and shorted the crystal along with other whiskers. We did a spectrographic analysis which showed that it was tin. As a result, the company I work for now requires spectrographic analysis of the internal structure on all crystals and oscillators before they are allowed to be used in production. Most of the products made by the company I work for are exempt but we can't buy new non-RoHS parts. We can get the leads gold plated but the inside is still tin so what do we do?

Go back to using lead!
For those of you suggesting how dangerous lead is to the environment: Really? How many people should die as a result of electronic failures due to the lack of lead? How many have already died? The original reason given to pull lead from electronics was the suggestion that lead leaches out of electronics in landfills and gets into the ground water. More recent testing indicates that was wrong (even in areas with the worst acid rain on the planet). Therefore, as long as you don't eat it, lead is not nearly the problem in electronic assemblies that most folks were led to believe.
Go back to using lead and require all electronics to be recycled - oh yeah, that's right, even with lead free electronics; we are still required to recycle.

So just exactly how much lead are these regulations actually keeping out of landfills? The only numbers that I have heard implied that there were about six pounds of lead in each PC that was scrapped. That sort of damaged the credibility of the claimers, at least as far as my belief in their veracity. I would ask the same questions about lead leaching out of landfills from electronics. My guess is that we see a lot more lead from demolished building materials that contained lead paint, which was in a more soluble form to start with. Besides all of that, putting a deposit on electronics the same as on deposit bottles, would have been a far less damaging way to keep them out of landfills. A $50 deposit on every cell phone and Ipod and similar devices would be much better for keeping that half gram of lead from reaching anyplace except a recycler. Am I the only one who has thought up this idea? Yes, of course the logistics might be a bother, but we could keep a higher level of reliability in all our electronic toys.

yes, sure, but that doesn't mean we shouldn't do it, just because it's too difficult. Manufacturers can't have it both ways: lead is a persistent, dangerous pollutant and MUST be kept out of the environment. We can either recycle it, or stop using it. One or the other.

Lead-free solder enforcement is a very poor thought decision. It should be limited to low reliability short-life toys.
The reasons are: the reliability and the fact that lead going properly to landfill is not a big problem. The harm is in compounds created, when incinerated.
So, with the toys likely to be thrown to furnace, the lead elimination is OK.
But not at all with properly recycled automotive electronics.
cheers
tomkawal

In case of Lead Acid batteries, then Lead is always in nice big chunks, so recycling is easy.
On a PCB it is in form of an alloy melted onto other metals, with a conformal coating on the top.
This makes recycling far more challenging.

Reduction of lead waste in the environment is the right thing to do. The problem was the way it was done. In hindsight, perhaps it would have been better to enforce rigorous re-collection of discarded PCBs for solder recycling (as is done with lead-acid batteries). It's not the environmentalists' fault if polluting industries fail to develop (or propose) better solutions for cleaning up their pollution.

No doubt Prof. Gilbert was correct and tin whiskers could be one of the causes for rare cases of sudden acceleration.
http://www.thetruthaboutcars.com/2010/02/dr-gilbert-explains-his-research-into-toyota-electronics/
excerpt
"What I have done is, I have shown that in the fault detection strategy of the Toyota systems, there is a window of opportunity where [an error] could occur and not be detected."
also see discussions in:
http://townhall-talk.edmunds.com/WebX/.f20003b/2011